Method of regulating and maintain



ture within the container.

Reissued Sept. 29, 1942 METHOD OF Henry E. Minor,

assignments, to tion, Chicago,

REGULATING AND MAINTAIN- G nan-r TRANSFER Dayton, Ohio, assignor, bymesne The Liquid Carbonic Corpora- IlL, a corporation of Delaware NoDrawing. Original No. 1,808,429, dated June 2, 1931, Serial No.

137,324 31 Claims. This invention relates to the method of controllingtemperature and more particularly the temperature of gas or other mediaunder pressure, for example as' is employed in the curing of rubbertires and the like.

The object'of the invention is to provide a simple and efficient methodof controlling temperature in curing, cooking, distilling underpressure, 'etc., and more particularly where an inert gas effect isdesired.

Further objects of the invention will appear more fully hereinafter.

My invention includes the discovery that by employing an inert gas underpressure in conjunction with steam under pressure any desired control ormaintenance 'of temperature conditions may be efiectedmhereby heattransfer and 252,676, February "I, 1928.

Application for reissue April 16, 1937, Serial No.

curing efiects, distilling under pressure, etc.,- can be economically,efliciently and readily efiected.

If any receptacle is supplied with a means for supplying an inert gassuch as CO: under pressure and another additional means for supplyingsteam at a fixed pressure both-lines being supplied with separatecontrols so that each may be supplied separately and used in amount asdesired, then, by varying the pressure and thereby the amount of inertgas supplied to the receptacle initially and then shutting ofi theinert'gas supply and-turning on the steam supply at a fixed pressure itis possible to obtain any desired tem-' perature condition from amaximum of the total available heat units contained in the steam at thefixed pressure down to a minimum where no steam and consequently noheatunits are added to the receptacle. container an inert gas as CO: isfirst admitted at an initial pressure of approximately 50 pounds and ifthe supply of CO2 is then shut off and steam is added to the containerat say 100 pounds pressure the first effect will be the resultantexpansion of the said CO2 within the container as As illustrative ofthis; if in a pounds. 20 pounds correspond to 260 F. 260 of temperatureis suflicient to cause the expansion of CO2 from 50 pounds to 80 pounds.Consequently a state of equilibrium has been reached which can bechanged only as a result of heattransfer. I Now if heat transferringoccurs within the container the effect of heat transfer will be to causeadecrease in temperature of the mixed gases. A decreased pressureresults and immediately the partial pressure of the steam is raised sothat additional heat units are available -'to maintain the temperatureequilibrium. From the. above it should be plainly evident that as aresult of my discovery temperature equilibrium can be secured andmaintained to suit any desired conditions.

It will be seen, therefore, that when an expansible gas is broughtintocontact with steam within an enclosed container (the DTBSBUIG 0f the1 gas being lower than that of the steam) the.

pressure within the container will be' the pressure of the steam. Partof that pressure,- howa result' of the direct contact with the steam.

This expansion will continue with increased pressure effect until thepressure of the G0; has in- 1 creased to the point where its pressurehad cut.

down the partial pressure of the steam supply to the point where thepartial pressure of the steam corresponded in temperature with thetempera- In other words in the above cited case (and this case does notpurport to be mathematically accurate but only illustrative) theCO-iwould probablyexpand to'about 80 pounds pressure as a result of thetemperature effect so that with steam maintained at 100 pounds pressurethere is] a dlflerential' of 20 55 ever, which I willterm the partial"pressure, is

made up by the two factors-(a) the cold initial pressure of the gas, and(b) the pressure of the gas expanded by the heat imparted thereto by thesteam. The partial" pressure within the I chamber attributal to the gasmay be varied at will by varying the relatively cold initial pressure ofthe gas. I

.- Inasmuch as the temperature of the gas ,mix-

"ture is dependent upon the partial pressure of the gas when expanded asa. result of the steam added thereto. and itis limited only by thetemperature corresponding to the partial pressure of the steam employedin conjunction therewith, by merely controlling the pressure of theinitial gas from a minimum to the maximum pressure of the steamemployed, I am able to effectively control the temperature of the gasand steam within the chamber. I Y

The practical applicability of'the invention is, therefore, readilyapparent. In all instances where heat transfer is desired my inventionpermits a simple econo-micaland extremely efllcient transfer of heatcontrolled solely by the pressure of inert gas employed. Where thepeculiar antioxidant and preservative efiectswell recognized for carbondioxide are desired the employ ment of this gas has an additionalfeature of enabling the utilization of such antioxidant and preservativeefiects.

I have discovered, furthermore, that not only am I enabled to obtain anydegree of temperature desired within the limit of the temperature of theheating media suchas steam employed with the inert gas, by merelycontrolling the pressure of the inert gas but I have also discoveredthat the temperature once established is automatically maintained.Variation in the partial pressure of the gas can occur only as theresult or giving up heat units with resultant temperature decrease.Variation in ti: 2 partial pressure. oi the steam can occur only as aresult of the condensation of the steam which occurs when heat units aregiven up. Thus in the example given, the partial pressure of the .gaswithin the receptacle will vary because of heat transfer from the gas orbecause of condensation of the steam in combination therewith. Anyvariation in the pressure of the gas steam mixture due to either of theaforementioned causes, causes a variation in temperature. Ifthetemperature decreases by reason oivariation of the partial" pressureof the gas additional heat units are automatically supplied by the steamincident to. the immediate increase of partial pressure of the steam; Inother words, the constant supply of the steam in any given set ofconditions in addition to the constant supply of the gas in any givenset of conditionsimparts an automatic valve effect which automaticallyestablishes a balanced condition within the container and maintains thatcondition.

In .eilect, therefore, I have provided an automatic valve forcontrolling and maintaining constant temperature and heat transfer ortemperature equilibrium whereby these factors may be efllciently andreadily controlled by the simple expedient of controlling-the pressureof the inert gas with respect .to a fixed steam pressure.

One advantage of the process is the relatively short time required tobring the mixture of carbon dioxide gas and steam to the desiredtemperature and the resultant even temperature which can be maintainedthereafter until the de? sired results are obtained. The particularadaptability oi the process in the curing of tires and tubes'ls evident.With the admission oi carbondioxide gas at a predetermined pressure, the

results can be accurately determined and madesired temperaturecontrolled with great accuracy. In'previous methods, as outlined above,a com .paratively long period of time has been required for raising thetemperature within the vulcanizer tocuring temperature, this beingespecially true in the vulcanizing oi rubber articles of considerablethickness or volume of rubber. With the combined use of carbon dioxideand steam in the manner herein set forth, the period of time requiredfor raising the temperature to the proper point ior'vulcanlzation isshortened materially, so

that the effective temperature for vulcanization is reached in ashortertime than possible with other methods which have preceded invention. The

process has the further advantage that the addition oi steam to thecarbon dioxide gas gives an acid reaction to'the mixture which isextremely beneficial in the vulcanization oi articles oi or.

containing rubber, giving superior ageing qualities, greater tensilestrength, superiortexhire and other advantages. r

The foregoing simple statement of the invention is in no sensecommensurate with the importance or extent of the industrialapplications thereof. The method described can be utilized in 'a greatmany ways and in a great many industries, While I willhereinai'ter.describe one concrete example, to wit; the curing of tubes and tires inthetireindustryglwlshittobeunderstoodthat' the invention can beequallyvwell applied in ourrubbershoe industry and in fact in curing anyrubber goods where longlii'e and decrease or minimizing of deteriorationdue to oxidation is desirable, or where the additional benefits aredesired to be obtained which accrue as a result of securing greaterdensity in rubber goods, more freedom from air bubbles and greateradhesion as a result of using higher pressures hitherto impractical. Iplied in pressure distillation operations, preserving foods, etc.Broadly stated, ,the invention may be utilized in any industry where itis desired to effect temperature pressure control under inert gasconditions. Similarly, while in connection with the example selected forillustration C0: is the inert gas selected, it will be understood thatmy invention is not to be limited or restricted in this respect, and anyfluid, liquid or gaseous,

(such as for example as alcohol or carbon dioxide) may be employed.

To enable a clear understanding ,of the applicability of my invention tothe art of curing tires and tubes, a -brief consideration will be givento the processes heretofore employed. It is, of

course, well recognized that the fundamental requirements in the curingof cord tires is that of uniformity of the product permittingequalquality particularly the larger sizes. The necessity for thisrequirement will be readily apparent when it is considered thatamanufacturer is ofiered scant opportunity to explain to a customer whohas a car equipped with four tires of standard make and who finds thatthe wear and life of the four tires is strikingly dissimilar. It is wellrecognized that difllculties in the curing of the tire are generally, ifnot always, found to be the cause. The two principal processesheretofore employed in the commercial curing of the tires are known asthe air-glycerine process and the "hot water process. In theair-glycerine process it is customary to add small amounts oi glycerineor other preservative to the air bag from time to time as a preventativeof oxidation. In curing with this process pressure is supplied with air.This process has the advantages of being relatively-simple, thelife ofthe air bag is not unduly shortened, and the time of curing is notunduly lengthened. The air-glyoerine process has its disadvantages,however. Leakage oi air into the heater from the manifold and. air bagconnections during the process of the cure is its. most objectionablefeature. In practice it has been found that tromtwo to four times asmuch air passes into the heater to mixwith steam as is actually requiredfor pressure purposes. Air

' settling to the bottom of the heater .causes undercuring-of thetiresand, likewise, tendewto form...

air pockets. Wherever air pockets occur a badly cured tire results.Furthermore, air mixed with steam interferes seriously with the heattransfer iromsteam to the mold. This condition has been one of the mostserious encountered in the rubber industry with the air-gl'ycerineprocess.

Some operators of this method endeavor to decrease the effect of thisserious disadvantage by agitating the steam mixture. Others blow oillarge quantities of steam from the bottom of the V heater to remove aireven though the expense of so doing ranges from $25.00 to $100.00 perday.

sun others both agitate the steam or mixture and blow off the steam.From these facts may be gathered the seriousness with which the disad-vvantages above enumerated inherent to the use at ing rubber boots,shoes, overshoes, etc., in the Likewise the same process may beapefforts to minimize the effects thereoff For ex- 5 ample, a dope ofsome kind to protect the inner surface of the air bag from the effectsof oxidation has been employed. The efiect of the dope, however, is tosoften the inner surface of the bagand in a measure this -must becompensated for by an added thickness of the bag, which in itself. isdisadvantageous. In adding .dope to an air bag there is a gradualaccumulation, and the amount will vary from bag to bag with respectivebags causing consequent variations in the tire cure, depending uponwhich bag is employed. Furthermore, the spitting of dope when removingold bags from tires causes further variation, loss, painful burns to theoperators and slippery floors thereabout, increasing the hazard ofoperating conditions as well as the inconveniencethereof, to say nothingof sanitary effects. Again, the air used to supply and maintain pressurefrequently carries water and oil with it so that on examination of anair bag at 5 the end of its life it is frequently found tohave a largevolume of a heterogeneous mixture of dope, oil and water, all of whichtend to shorten the life of the bag. Likewise, the last tires cured bythat bag receive a very different cure from those when the bag was new.7

The hot water process was not extensively adopted until quite recently,principally because it was diflicult to induce the installing of adifferent process which did not ofier any apparent advantage from aviewpoint of air bag life and air bag cost over the air-glycerineprocess, especially Where such installations and maintenance wereexpensive. This process, however, has the advantage of enabling curingfrom two sides thus permitting a quicker cure. With the advent ofthicker tires, made necessary by the phenomenal growth of buses,however, the hot water process began to be generally adopted. Witheight, ten,

and twelve ply tires in daily production by the large tire manufacturersit is obvious that where heat is supplied from the outside of the tire(as in the air-glycerine process) the inner plies of the tire are goingto be in an uncured state. In

the hot Water process it is customary to'apply all of the pressure withhot water, air being removed from the bag by an initial application ofsteam which also serves to raise the initial temperature of the air bag.This process, like the air-glycerine process, has its advantages. The,additionof heat units to the insideog the bag ,so that curingprogresses from two sides towards the center ismanifestly an advantage,particularly in view of the bus tire development. Likewise, the hotwater system obviates the principal disadvantage of the air-glycerinesystem because when hot water is used as the pressure medium there willbe no leakage of air from the manifold and bag connections to mix withthe steam in the heater. from the steam to the mold are superior to whatare obtained in the air-glycerine process.

The,,disadvantages of the hot water process, aside from its high cost ofinstallation and maintenance, reside in-the poor relative life obtained70 from the air bags ue to th weakening effect of water and the bartreatment of the bags themselves by reason thereof; wet floors andtables, the necessity of evacuating the bags with a costly vacuumsystem, the cost of raising the water to 7 Consequently the transfer ofheat units a high temperature and pumping it at a high temperature-thehazard attendant to its use, and the eflfect of only a slight leakagewhen the medium pumped is of an incompressible nature. Furthermore,while water transfers heat rapidly at the start, it rapidly-cools off,and it is not possible to maintain uniform temperature conditions withinth air bag.

A third process, known as the carbon dioxide process" has recently beenthe subject matter of considerable comment and experiment in the art.The claimed advantage therefor have been that the bagwould be dry at alltimes, permit a more uniform cure than that obtained with theairglycerine process and enhance the air bag ,life. On the other hand,the objectionable features of gas leakage into the steam of thevulcanizer remains and this process offered nomeans for adding heat tothe inside of the tires. Thus the most that was urged for the carbondioxide process was that a slight saving was secured over theairglycerin process. 1

The application of the process of my present invention enables securingthe advantages of the air-glycerine process, the hot water processandthe carbon dioxide-process with complete elimination of thedisadvantages of all, as applied to the curing of cord tires, forexample in a pot heater, or as applied to the Curingof molded tubes inindividual or multiple type heaters. Thus, applying the principle of myinvention to this particular industry, the receptacle in this instancewould be the bag and the process would consist in first bringing up apart of the pressure with an inert gas such as 002 to a predeterminedpressure, then shutting off the gas and turning on steam at the curingpressure and leaving it on throughout the period of cure. The firsteffect of the steam is to heat up th inert gas, as hereinbeforeexplained, causing it to expand thus cutting down the partial pressureof the steam that can enter at the bag thereby insuring an innertemperature of any desired amount which may be easily computed for anydesired case.

It will be understood thatthe values for the pressure and temperaturewill vary according to the surrounding conditions as well as theparticular type of material being treated or cured.

I will give two examples which are approximately standard conditions metin the 'art.

Fmsr EXAMPLE.'-In the curing of tires where two hundred pounds internalpressure is ordinarily used.-In thisexample let us assume that it isdesired to efiect curing of tires at 260 F. or

20 pounds gauge pressure, and the pressur maintained on the'air bag andthence to the tire in the mold is 200 pounds. The factor to bedetermined is the proper gauge pressure of the CO; which when backed by200 pounds of steam will maintain the same curing temperature within thebag as exists without the mold. 200 pounds gauge pressure isapproximately eriual to 215 pounds absolute pressure. Steam having atemperature of 260 F. is equivalent to 20 pounds-gauge pressure of steamor '35 pounds absolute pressure. Inasmuch as the maximum absolutepressure in the bag will be 215 pounds (the absolute pressure of thesteam) and the desired temperature-tosmall and the cost e b etemperatureof CO at 260 F. is approximately 720 absolute. solute partial pressureof the gas and the absolute temperature of the gas at its originaltemperature divided by the absolut temperature of the gas at the desiredtemperature of th bag (to wit: 720 absolute) gives the absolute pressureof the gas at its original temperature (to 'wit: 100? F.) required toestablish and maintain within the bag a temperature of 260 F. This yaluein the example given is 139.86 absolute pressure'which' is equivalent toapproximately 125 pounds gauge pressure. Therefore, to meet theserequirements, employing steam at 200 pounds gauge pressure andestablishing and maintaining a temperature within the bag of 260 F. CO:at a gauge pressure of 125 pounds is employed.

Ssconn E1IAMPLE.I7Z the curing of tubes where Therefore, the product ofthe abone hundred pounds internal pressure is ordi- I narily used,desired temperature 260 F.Assuming the ame curing conditions as in thepreceding example, then 100 pounds gauge pressure of steam is equivalentto 115 pounds absolute pressure. The pressure of steam equivalent to 260F. is pounds gauge pressure or 35 pounds absolute. Subtracting theabsolute pressur of the steam at the desired temperature from theabsolute pressure of the steam supplied determines the partial pressureof the CO: under the desired conditions-to wit: 80 pounds absolutepres-- sure. Again, assuming the original temperature of CO2 is 100 F.or 560 absolute, then the temperature of the CO2 at the'desiredtemperatureto wit: 260 F.-is equivalent to 720 absolute and theproduct of the partial" pressur of CO2 and of the absolute originaltemperature of the CO1 divided by the absolute temperature of CO: at thedesired operating temperature is th absolute pressure of the C02required. In this instance 62.2 absolute pressure results or 47.2 gaugepressure. From the foregoing it will be seen that any desiredtemperature. or pressure conditions example, in the actual curing ofsome molded tubes tensile tests showed the following results:

tubes cured on" air a tensile of 3025 pounds; tubes cured on CO2 atensile of 3100 pounds; tubes cured on CO2 and steam tensile of 8375pounds. These same tubes after-be1ng aged six days in the Geer Oven showtube cured on air tensile 3400 pounds; tube cured on (3013575 pounds;tube cured with CO: and steam tensile 3900 pounds.

The amount of inelt gas used is relatively ,In general only one-third ofthe pressure is. supplied with gas" and, if desired, two-thirds of thismay be easily recovered for reuse. .By employing steam in lieu of air asubstantial reduction of cost is effected inasmuch as the air ordinarilyused in curing tires costs approximately l per tire while steam By usingsteam for an added and maintaining prescosts less than 50 per thousandpounds.

as those at the top (in pot heaters holding from twenty to thirty tirespiled one on top of the other). This has constituted one of the mainadvantages of the hot water process. There is no accumulation in the airbag and consequently the cure 'does not vary between different bags asin the air-glycerine process. -The pressure means employed beingentirely gaseous permits the complete function by the blow down at theend of the cure. This eliminates the necessity of collapsing the airbags by a costly vacuum system as in the hot water process. with itsloss of time and its weakening effect on the bags.

Carbon ,dioxide increases air bag life. This gashas been used in thepast .on niany-and all kinds of air bags when it has been proven inpractice that the presence of gas black in large amounts reactsunfavorably with carbon dioxide, the bag becoming porous and the gasblack. at curing temperatures acting to break down CO2. Iron oxide alsoacts in asomewhat similar manner. The bag should be preferably of someother mixtures. Practically all tests in the past have been made withgas liquefied at high pressure in cylinders and the users have notstopped to consider that this product was an excellent dehydratingagent. So long as the air bag is, not used beyond heats it is not soimportant but beyond this point the cumulative effect of a dehydratingagent becomes increasingly evident both in thejsuperficial ap pearanceof the interior of'the bag and in its physical characteristics. Thediscovery that carbon dioxide should. be used moist in orderv to secureits most desirable characteristics was one of importance. Underfavorable conditions C02 increases the life of air bagsfrom 20% to 30%.

'. Assuming an air bag of one-half cubic foot sure in the bag theleakage of air into the heati ers is entirely eliminated. Likewise, byeliminating air in the heate the tires at the botvolume. If the hotwater is added at a temperature of 350 R, which during the cure drops toa temperature of 250 F.', the total'number of B. t. u. available is62%/2 100= 3l21 B. t. u. If in the employment of my present inventiononly- 4 pounds of steam are condensed 4000 B; t. u. are released forheating and there is a. vast practical diiference between removing 30.odd pounds of water on the one hand and removing a matter of four pintsat the most. As. a matter of fact, fewer heat units are needed to beadded to the bag when employing my invention because of the reducedthickhess thereof required as compared with thethickness'of the bagemployed in the hot water process.

As a further illustration of the applicability of the process of myinvention attention may be called to the advantages secured by the useof this process in the manufacture of molded tubes. The employment ofthe process of y present invention to the curing of molded tubes hasenabled a 25% reduction in curingtime required and the quality of thetubes produced inaccordance therewithhas been found o be consistentlyuniform' and outstanding as compared with tubes cured by any otherprocess.

It will, therefore, be readily understood from the foregoing that Ihave'provided a simple and highly eilicient method far reaching in itseffect and scope in industrial application. The principle of the processpermits of wide and varied application. Attempts have been made in thepast to utilize steam for curing purposes secure the beneficial effectsof using an inert gas, and eliminating the disadvantages of usingincreased steam pressure by being able to control at will thetemperature of the mixture within the chamber wholly irrespective of thetemperature of the steam correspondingto the pressure utilized.

Having now set forth theobjects and nature of my invention and havingset forth the principles upon which it is based, as well as anapplication thereof by a specific industry, what I claim as new anduseful and of my own invention and desire to secure by Letters Patentis:

1. The method of controlling temperature for pressure of steam desiredand at the same time heat transfer which comprises supplying carbondioxide to a receptacle and controlling the pressure of the carbondioxide, supplying steam. to said receptacle at apredetermined-pressureand supplying additional steam as required to replace the heat lost.

2. The method of controlling temperature for heat transfer whichcomprises supplying carbon supplying steam to said receptacle at apredetermined pressure and continuing to supply steam as required'tomaintain the desired temperature.

3. The method of establishing a heated medium for heat transfer whichcomprises supplying a fluid to an enclosed receptacle and supplying aheated fluid at a higher pressure to said receptacle, shutting off thesupply of said fluid and maintaining the supply of heated fluid wherebydioxide to a receptacle in the desired amount,

the pressure of the heated fluid and the pressure of the first fluidtogether with the pressure resulting from theexpansion of the firstfluid through contact with the heated fluid equals the maximum pressuresupplied to the receptacle,

and preascertaining the pressure of the first fluid to obtain thedesired temperature within the receptacle.

4. The method of establishing a heated medium for heat transfer whichcomprises supplying carbon dioxide gas under pressure to an enclosedestablishing the pressure of the carbon dioxidegas supplied to thereceptacle so that the corresponding partial pressure of the steamwithin the receptacle is of a value corresponding to that of the desiredtemperature. s

5. The method of controlling temperature for heat transfer whichcomprises supplying an inert gaseous fluid to a receptacle under apredeterthereof, then continuously supplying a relatively hotter gaseousfluid tojsaid receptacle at a. predetermined pressure.

6. The method ofcontrolling temperature for mined pressure, thenshutting off the supply a dioxide to a receptacle at a predeterminedpressure, then shutting off the supply thereof and supplying steamthroughout the process to said. receptacle at a relatively greaterpressure,

7. The method of curing rubber tubes which 7 comprises admitting carbondioxide under pressure to the interior thereof, shutting off the supplyof the carbon dioxide, then continuously admitting steam under arelatively greater pressure tothe tube, the pressure of thecarbon'diconsists of expanding a gas within a container by thesubsequent and maintained addition of a heated vapor at a highertemperature and pressure.

9. The method of'obtaining and maintaining a desired temperature byfluid pressure which of fluid pressure which consists in supplying a gasat a predetermined pressure to a heat transfer chamber, abutting off thesupply of said gas, then supplying a heated fluid at a higher fixedpressure to said chamber, and maintaining the supply of said heatedfluid to automatically compensate for loss of heat units within saidchamber.

11. In fluid pressure heat transfer systems, the step of initiallyutilizing a gas for reducing the partial pressure of a subsequently andcontinuously supplied heated vapor at higher pressure.

12. The method of utilizing fluid pressure to obtain and maintain adesired temperature for heat transfer which comprises supplying a gas toa container, then supplying aheated fluid at greater pressure to saidcontainer and finally utilizing the heated fluid alone to replace heatunits lost in said container.

13. The method of obtaining and maintaining a. desired temperature 'forheat transfer which comprises. supplying a gas and a'heated fluid to areceptacle and utilizing a continuous supply of heated fluid to saidreceptacle alone for maintaining the temperature within said receptacle.

14. The method of obtaining and maintaining adesired temperature forheat transfer by means of fluid pressure which comprises admittingcarbon dioxide and steam into a closed'receptacle and maintaining theresultant temperature within said receptacle by a continued supply ofthe steam alone. I

15. The method of obtaining and maintaining a desired temperature withfluid pressure which consists of expanding a gas within a container bythe subsequent and maintained addition of a.

heated condensible vapor at a higher temperature and pressure.

16. The method of obtaining and maintaining a desired temperature withfluid pressure which consists of expanding a gas within a container bythe subsequent and maintained addition steam at a higher temperature andpressure.

1'1.'The method of obtaining and maintaining a desired temperature forheat transfer by means of fluid pressure which consists in supplying agas at a predetermined pressure to a heat transfer chamber, shutting offthe supply of'said gas,

heat transfer which comprises supplying carbonthen supplying steam at ahigher fixed pressure and maintaining the supply of said steam toautomatically compensate for loss of heat units within said chamber.

18. In fluid pressure heat transfer, the steps of utilizing a gas forreducing the partial pressure on rubberarticles being cured in areceptacle and of subsequently and continuously supplying steam athigher pressure to said recepa desired temperature for heattransferwhich comprises supplying a gas and steam to a receptacle andutilizing a continued supply of steam alone for maintaining thetemperature within receptacle.

21. The process of vulcanizing rubber articles under internal pressure,comprising introducing into the article inert gas at a predeterminedpressure, subsequently connecting the interior of the article with asource of steam to the said article at a pressure greater than thepressure of the inert gas, and maintaining'the connection with the steamduring the process of vulcanization. 1

'22. The process of vulcanizing rubber articles under internal pressure,comprising introducing into the article inert gas at a predeterminedpressure, subsequently connecting the interior of the article with asourcofi-steam at a pressure greater than the pressure of the inert gas,

and maintaining the temperature within the article constant during theprocess of vulcanization by the'addition of steam under pressure.

23. The process of vulcanizing rubber articles under internal pressure,comprising introducing within the article inert gas at a predeterminedpressure, adding steam under pressure to raise the temperature of thecontents of the article to a fixed curing temperature, and continuingthe steam supply to replace heat units lost in the process ofvulcanization.

V 24. The process of vulcan-izing rubber articles comprising subjectingthe articles to inert gas at a predetermined pressure, adding-steam at ature by additional increments of steam.

26. In the process of vulcanlz'ing articles by a mixture of steam andinert gas under pressure and at the desired temperature, comprising sup-27. In the vulcanization of articles of or containingrubber, the stepsof subjecting thearticle to a mixture of carbon dioxide and steam, the

steam being supplied at atemperature higher than that required forvulcanization, the carbon dioxide and steam being supplied at differentinitial pressures, the differential in pressure of: steam over carbondioxide determining the temperature of the mixture at whichvulcanization is to be carried on. i

28. In the vulcanization of articles of or containing rubber, the stepsof subjecting the article to a mixture of carbon dioxide and steamsupplied at different initial pressures, the differential in pressure ofsteam over carbon dioxide determining the temperature of the mixture, atwhich vulcanization is to be carried on,

and replacing lost heat units and pressure by the addition ofhigherpressure steam in .the

29. In heat pressure methods of treating articles of or containingrubber, including the vulcanizing process, the step of subjecting thesame higher pressure toraise theinert gas to'vulcanto' carbondioxidebrought to vulcanizing temperature by the introduction thereinto ofsteam under pressure. V

30. In the method of curingrubber articles, the step of subjectingrubber articles in a recep- I 'tacle to the combined action of carbondioxide and steam.

31. In a method of curing rubber tires, the steps of (a). separatelyintroducing gas and vapor, (b) using the heat of the vaporior curing,(0) using the ,gas for maintaining'pressure during the cure, and (d) sointerrelating the 88$ and vapor that the gas will prevent-the vapor,

from over-curing the tire. and the heatfrom the vapor will increase thepressure of the gas.

' HINRY R. MINOR.

